Many medical and surgical instruments and apparatuses must be cleaned, disinfected and sterilized after use. Cleaning and disinfection are conventionally carried out in so-called automatic washing/disinfecting machines. In these machines the instruments are cleaned, disinfected and dried in preparation for subsequent sterilization.
It is a requirement of the German Law of Medical Products, and comparable regulations in other countries, that the mechanical cleaning process used should be checked for efficiency. On the one hand, this embraces a homologation of the process, which the manufacturer of the automatic washing/disinfecting machine has to undertake before it can be marketed. On the other hand, the user must check the cleaning power of the machine at regular intervals.
To check the cleaning power, so-called test samples with defined test stains are required. The most stubborn stain on medical and surgical instruments and apparatuses, and the one which is hardest to remove, is normally coagulated blood.
In the prior art the homologation to be undertaken by the manufacturer is therefore often carried out with fresh human blood as the test stain. Fresh blood is required because stored blood has had its coagulation reduced by the addition of anticoagulants. However, it is not practicable for the user to employ fresh human blood for regular checking of the cleaning power.
The prior art (established prior use) therefore proposes a variety of test stains such as semolina, egg yolk, starch or stains containing flour. As the properties of all these test stains are markedly different from those of blood, the evidence obtainable on the efficiency of the cleaning process in respect of bloodstains is nonexistent or at best imprecise.